Field of the Invention
The present invention relates to three-way catalytic control, and more particularly, to a three-way catalytic control method and system for decreasing fuel consumption by oxygen gas (O2) purge control of the three way catalyst and a vehicle having the same.
Description of the Related Art
In general, exhaust emission and environmental regulations require reduction of pollution control materials such as nitrogen oxide (NOx), carbon monoxide/hydrocarbons (CO/HC) and the like, and thus vehicles are equipped with a catalyst such as Diesel Oxidation Catalyst (DOC), Catalyzed Particulate Filter (CPF), Selective Catalyst Reduction (SCR), Three Way Catalyst (TWC) and the like.
A three-way catalyst, inter alia, is useful in gasoline engines since such catalyst embodied with precious metals (e.g., Pt/Rh, PD/Rh, or Pt/Pd/Rh based metals) can participate in both oxidation of CO and HC and reduction of NOx and when an oxygen storage capacity material (hereinafter, the “OSC”) is added thereto, improve performance of purifying CO, HC, and NOx. As an example, the three-way catalyst applied to gasoline engines, which may be classified as a new product, a deteriorated product, and On Board Diagnosis (OBD) based on oxygen concentration content of OSC, is adjusted by an O2 closed-loop control which is executed in connection with an oxygen detection amount of an oxygen sensor (hereinafter, the “O2 sensor”), and increases CO, HC oxidation performance on condition of high oxygen concentration content of OSC and improves NOx reduction performance on condition of low oxygen concentration content of OSC.
Particularly, the new product stands for an unused three-way catalyst under the state that activity of precious metals is high and an oxygen storage amount of OSC is high, the deteriorated product stands for an used three-way catalyst in which deterioration of the catalyst has occurred, and the OBD stands for a catalyst used for an extended period of time, in which an oxygen storage amount of OSC defined as a set value of OBD is detected upon OBD monitoring. Therefore, the oxygen storage amounts of OSC increase in the order of a new product>a deteriorated product>OBD while time periods for O2 closed-loop control also increase in the order of a new product>a deteriorated product>OBD. The symbol “>” is an inequality sign indicating the magnitude relationship between two values.
Therefore, the O2 closed-loop control for the three-way catalyst realizes increasing NOx purification performance after fuel-cut of gasoline engines under which a low oxygen atmosphere (hereinafter, the “LEAN”) is converted into a temporary high oxygen atmosphere (hereinafter, the “RICH”). Particularly, the fuel-cut is executed at a section of decreasing speed and the like to improve fuel economy. However, since the O2 closed-loop control for the three-way catalyst is performed based on an oxygen detection amount of the O2 sensor, a control time period must be used to which characteristics of the three-way catalyst having optimum performance or the relatively highest oxygen detection amount are not reflected.
For example, when the three-way catalyst is a new product, its characteristic is that since activity of precious metals in the new product is excellent, NOx may be sufficiently removed through reaction of the precious metals even though oxygen storage amount of OSC is high. Therefore, a control manner that increases a control time period for O2 closed-loop control to be greater in a new product than that in a deteriorated product simply stands for increasing only the time period during which oxygen stored in OSC of the new product is removed, without contributing to NOx reduction.
In particular, the O2 closed-loop control increases fuel consumption amount such that the atmosphere in combustion chambers is converted from LEAN to RICH. Accordingly, increase of the time period for the O2 closed-loop control in gasoline engines of vehicles equipped with a new product leads to an increase of fuel consumption, and thus the O2 closed-loop control leads to reduction of fuel economy contrary to fuel-cut and in turn the reduction of fuel economy is difficult to meet the enforced environmental control requirements.